Impedance-phase reshaping of LCL-filtered grid-connected inverters to improve the stability in a weak grid

The stability of grid-connected voltage-source inverters (VSI) is deteriorated in a weak grid due to the interaction between the increasing grid impedance and the inherent inverter impedance. To improve the stability of LCL-filtered VSI, an impedance-phase reshaping method is proposed in paper. With this output current feedback compensator, the phase margin at the impedance intersection can be improved dramatically. A straightforward parameter design method is also introduced to simplify the design procedure. Simulation and experimental results valid the effectiveness of the proposed the method and design methodology.